Prof Nick Fox, from the National Hospital for Neurology and Neurosurgery in London, says focusing on earlier treatment is "absolutely critical to research".

Developments have been made. It is now possible to see one of the damaged proteins closely tied to Alzheimer's disease in brain scans, but the challenge is to use these tools to predict the development of dementia.

"There have been huge advances in brain imaging, it's a new era and it is very exciting," said Prof Fox.

Other methods, such as finding chemicals in the blood which might predict the onset of dementia, are being investigated as well.

Dementia is also not one disease, but many. Alzheimer's disease, vascular dementia and dementia with Lewy bodies all have similar symptoms, but may need different treatments. Scientists will need to come up with techniques which can readily distinguish between different forms of dementia.

Stop brain cells dying

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There is no drug which can halt or even slow the progression of any form of dementia.

A lot of hope was placed on two potential Alzheimer's drugs - solanezumab and bapineuzumab - but they failed in trials which showed no benefits for cognition.

However, there were hints that solanezumab may work in people with the earliest stages of the disease.

A new trial has started looking at patients with mild dementia.

Dr Eric Karran, director of research at Alzheimer's Research UK, said that if it was shown to work then the drug may be used in a similar way to statins for heart problems.

"I think the pathway now is if solanezumab is shown to work in mild Alzheimer's disease then the pathway would be to give it earlier and earlier and earlier... and you could have confidence you will see an effect."

A cure is obviously the dream, but just slowing the pace of the disease would deliver massive rewards.

Delaying dementia by five years could halve the number of people living with the disease.

Develop drugs to treat the symptoms

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Memantine was the last new dementia drug

There are dementia drugs, which help people to live with the condition, but there are not enough.